The weapon used in the killings has been a mystery for decades.
The knife is being analyzed by an LAPD crime lab. Neiman said investigators didn’t know the identity of the person who handed it over and asked him or her to come forward.
The killings occurred on June 12, 1994, and led to the “Trial of the Century” in which the former football star was acquitted in October 1995 by a jury that deliberated only four hours.
In 1997, a civil court jury found Simpson liable for the slayings and awarded millions of dollars in damages to families of the victims.
Neiman did not believe that Simpson could be charged again with murder if the knife is linked to the killings, citing double jeopardy.
“I’m not an attorney but it’s my understanding from being a police officer for nearly 30 years that double jeopardy would be in place here,” he said.
Simpson is imprisoned in Nevada for a 2008 armed robbery and kidnapping conviction.
The account of the knife’s discovery was first reported by TMZ.